1. Field of the Invention
The invention relates to a video processing method, and more particularly to a method for video enhancement.
2. Description of the Related Art
Digital video monitoring has become an important object based on development of the science and increment of requirements for public security maintenance. A video camera is installed with a video enhancement module to enhance video quality, processing brightness, saturation, noise, or edge features to picture clear frames under a dark, dense, or defocusing environment.
Prior video enhancement methods consider pictured frames as respective independent images so quality of the respective images can be improved. A single image can be enhanced using a global enhancement method or a local enhancement method. The global enhancement method sets a color conversion function, which is user-defined or implemented using a statistical method, and adjusts colors of each pixel of the image using the color conversion function. Common global enhancement methods comprise Contrast Stretch, Histogram Equalization, and so on. The local enhancement method determines enhancement degrees of respective pixels of an image based on local features of the image. Additionally, distances of the depth of field of respective pixels of the image can be predicted based on pixel units and colors of each pixel are compensated using an optical model.
The global enhancement method is capable of rapidly operating, saving memory space, and being easily to be implemented but does not provide features of a local region, such that over-enhancement or unacceptable quality of the local region. The local enhancement method can result in applicable effects but consume large operation resources due to greatly accessing local pixels or calculating enhancement coefficients by multiplication/division or logarithm. Recently, known video technology improves quality of video enhancement using multiple images but accelerative processing is less developed.
With respect to the development of vide applications, the global enhancement method providing low amount of operation has been widely applied, such as auto white balance (AWB) used in a video camera. In order to handle growing requirements for video hardware and software, a method for effective and rapid video enhancement is desirable.
With respect to video monitoring applications, video capture equipment (such as a video camera) generally takes specified scenes at a static or periodically dynamic state. Some conventional video enhancement methods independently process respective images (frames) and does not consider the temporal similarity of an image, such that enhancement coefficients of static regions of the image is re-calculated. Thus, technology for combining multiple images to enhance video quality has been disclosed but reducing operational complexity seems not to be discussed.
Additionally, prior calculation processes of enhancement coefficients indicate the bottleneck of the local enhancement method and, however, can be improved to substantially reduce operation amount of the video enhancement.